When Facebook launched on February 4, 2004, Mark Zuckerberg was a 19-year-old sophomore at Harvard. Today he isn't even 30 and he's worth billions of dollars.

It's hard to believe how young he was when he got started. Here are some photos of young Zuckerberg for Throw Back Thursday (Twitter and Instagram slang fondly known as #TBT, where people post old photos of themselves).